Corrosion resisting alloys



Patented June 12, 1 934 UNITED STATES PATENT OFFICE CORROSION RESISTING ALLOYS William H. Keen, Albany, N. Y., assignor to Chas. W. Guttzeit, New York, N. Y.

No Drawing. Application June 11, 1932,

Serial No. 616,753

' 18 Claims.

the cost of the same prohibits their use commerl6v cially for structural beams and plates and in other applications where the tonnage is high. Such steels, especially those of higher ranges of chromium, tend to have low strength and low resistance to impact. I have discovered that the amount of chromium and, therefore, the cost of the steel can be materially reduced if magnesium is present with the chromium. The quality of the steel can also be improved whether containing high or low chromium content, if magnesium 55 and nickel are added. For example, in steels containing from 1.5% to 7.5% or more of chromium and 0.25 to nickel the presence of magnesium in amounts from 0.05% to 3% adds to the corrosion resisting properties more or less in proportion to the amount of magnesium present. Increase of magnesium beyond 3% is probably of no substantial advantage or disadvantage. The present invention has been developed more particularly in connection with the production of corrosion resisting steels suitable for use in the manufacture of cutlery and the like and for boiler tubes, rolled plates, sheets and the like, such as used for roofing and inthe manufacture of freight cars and especially tank cars, and for m convenience of disclosure such embodiments of the invention will be described. The description, however, is illustrative merely and is not intended as defining the limits of the invention.

An alloy steel suitable for rolling or. forging and having corrosion resisting properties may contain, for example Per-cent Carbon .01 to 1 i0 Chromium 1.5 to 20 Magnesium .05 to 3 Calcium .15 to 3 Aluminum 0 to 3 Nickel 0.25 to 10 i5 Iron the remainder For steel to be .used in the manufacture of structural steel, rolled plates and the like, the chromium may ordinarilybe kept between 4% i0 and 7.5% to obtain desired quality, without too great expense. For cutlery steel a range of 10-15% chromium is more satisfactory.

For applications where a slight superficial rusting is not objectionable, a composition represented by the following would be satisfactory, easy to manufacture and low in cost:

' Per cent Carbon .05 to .15 Chromium 4.0 to 8.0 Nickel .50 to 3.50 Magnesium 1 .10 to .80 Iron the remainder Material of this type is valuable not only from point of view of excellent physical properties, but more especially from consideration of its durability and low cost. It should meet with.

considerable favor in replacement of ordinary steel for use in manufacture of fabricated articles required for many very common applications where deterioration is rapid as for instancestor- ,age tanks, steel freight cars, tank cars, ships,

roofing, fencing, wheelbarrow bodies and miscellaneous products.

When acorrosion resistant material of moderately low cost is desired, with added requirement of great malleability such as would be necessary to stamp or spin into complicated and distorted shapes from sheets or strip, a com- Obviously the cost of this alloy would be higher than the preceding one on account of the higher nickel, but it would not be nearly as expensive as the corrosion resisting steels now on the markets as for instance, the 18% straight chromium alloy, or the 18% chromium, 8% nickel material, andshould fill the requirement fora low priced steel suitable for numerous applications where rusting and deep pitting is now tolerated but is exacting a heavy annual replacement toll.

A steel of this character with chromium in the lower partof the range indicated while not necessarily having as effective corrosion resisting properties as the best corrosion resisting chromium steel, will nevertheless withstand the eifects of corrosion perhaps three or four times as well as the steel now used for structural work and the like, and yet the cost will not be prohibitive.

An increase of chromium improves the corrosion resisting properties but adds to the expense. Such elements as vanadium, molybdenum, tungsten or tantalum may be advantageously added for the usual purposes and do not substantially change the corrosion resisting properties of this'steel.

An excellent steel for all cutlery may be of the analysis:

Percent Iron Chromium 11 to 13 Nickel 1 to 2 Magnesium .30 to .80

If the carbon approximates .10%, this steel can be cold rolled to provide a sufficient hardness and then stamped out with dies. If the carbon is higher, it may be first manufactured and then hardened.

Manganese and silicon may be varied within the usual. limits as in ordinary or stainless types of steel according to specificationdesired without any marked effect upon corrosion resistance. Deoxidants such as zirconium, aluminum, calcium, boron, and titanium may be used, in the usual way, but are not essential to the quality of the steel.

The addition of magnesium to corrosion resisting steels of higher chromium content is also beneficial and improves their stain resisting properties to a noticeable degree. This improvement is especially noticeable in improved resistance to attack of acetic acid, a factor of importance in steel for tank cars carrying vinegar, pickles and the like. The improvement is also apparent on the copper sulphate test which is now being employed by many users of steels of this type. Benefits are noted even with very small amounts such as are barely determinable by chemical analysis, but are more marked with increasing quantities on up to 1.5% and 2%.

The effect of calcium is not entirely understood but it acts in some respects like magnesium and may be grouped with magnesium for some purposes though not entirely as an equivalent. As the proportion of calcium is increased the proportion of magnesium may if desired, be decreased, but this is not considered necessary.

Nickel in the alloy inhibits grain growth. While it is generally considered a toughening agent, in amounts up to 3 or 4% it also causes an increase of the elastic limit and in hardness by.causing small grain structure and in larger proportions it causes a ready conversion to austenitic structures with a resulting toughness.

The toughening effect is perhaps of more importance in the high chromium alloys which lack toughness for forging at high temperatures. An optimum addition to a 14 to 20% chromium steel would consist of approximately 3% nickel and 0.50% magnesium, the nickel being increased in case deep drawing qualities are desired.

When the carbon is high, as for example above .20% or more specifically in the range of .30 to 50%, the nickel gives very definite and decided air-hardening effect, especially when present in an amount approximating 3%. Such a composition is highly resistant to abrasion. This improvement in air-hardening is more advantageous in steels having a chromium content of approximately 12% or more.

A higher nickel content, for example up to 12%, also improves the corrosion resistance and provides an effective alloy for the construction of tank cars and for similar uses. The range of 6 to 10% nickel with 0.30 to 0.80% magnesium is perhaps best so far as corrosion resistance is concerned. Such an alloy, especially with nickel in the higher part of the range, is ductile and will stand distortion. With low carbon and high chromium a very effective alloy for cold drawing, spinning and similar deforming operations is provided.

In the manufacture of this steel the elements should in general be added in the usual manner, but it is desirable that the magnesium be added shortly before pouring when the steel has been properly killed and the temperature is about right for tapping. A small area of the bath should be cleaned of slag by means of a scraper and the magnesium added directly to the metal. Tapping should follow as soon as practicable to avoid undue loss of magnesium. Ordinarily the addition of pure magnesium metal is impractical. In some respects the ideal alloy to be added would be a composition of magnesium and iron, but up to the present time no one has been able to produce a ferro-magnesium alloy. Since the final alloy in the present case includes both nickel and magnesium, the readily obtained nickel magnesium is perhaps the most desirable alloy to add in practice when introducing a part or all of both the magnesium and the nickel. However, some of the more common alloys such as aluminumsilicon-magnesium, aluminum-magnesium, or magnesium-manganese-silicon may effectively be added. The use of a compound containing aluminum has the advantage that the presence of aluminum also improves the corrosion resisting properties and permits a reduction of the percentage of magnesium to obtain the same degree of corrosion resistance. A mixture of several alloys may be added, if desired. Calcium may be added with the magnesium or the magnesium omitted and calcium alone added before tapping.

Conveniently the calcium may be added in the form of calcium silicide, or some other alloy such for example as nickel-calcium which could be conveniently produced by a method similar to the Hall process of reducing aluminum except that in this case the calcium would be reduced by electrolysis from a molten bath of a calcium salt as for instance calcium chloride, into a cathode of molten nickel or any other element desired for the resulting alloy.

It is of interest to note that steel of the character described will withstand exposure over long periods at elevated temperatures. At 1700 Fahrenheit, for instance, there is no appreciable oxidation.

The steel described may be readily rolled into structural shapes, plates, sheets and the like, and

especially in the lower chromium range it can be produced at a cost which is more than justified by the greater durability.

The following analyses of typical steels which have been found suitable for rolling into plates, sheets, and the like, are illustrative:

These analyses are illustrative merely, of steels which would meet the physical requirements for tonnage applications.

' Good malleable steel for cold drawing or spinning operations may be of the analysis;

Per cent Iron 73 Carbon .06 Silicon .20 Manganese .32 Sulphur .02

Phosphorous .02 Chromium 16.00

Magnesium 0.50 Nickel 10.05

An illustrative cutlery steel analysis:

' Per cent Iron 83 Carbon .40

Silicon .15 Manganese .29 Sulphur .025 Phosphorous .023 Chromium 13.50 Magnesium .42 Nickel 1.50

1. A corrosion resisting steel containing approximately 3 to 20% chromium, 0.25 to 10% nickel, 0.15 to 3% of magnesium, with the remainder substantially iron.

2. A corrosion resisting steel containing approximately 4 to 7% chromium, 0.25 to 5% nickel, 0.15 to 1% of magnesium, with the remainder substantially iron. 1

3. A corrosion resisting steel containing approximately 3 to 7.5% chromium, 0.25 to 10% nickel'and 0.10 to 3% magnesium, with the remainder substantially iron.

4. A corrosion resisting steel containing approximately 5% chromium, 3% nickel and 1% magnesium, with the remainder substantially iron.

5. A corrosion resisting steel containing approximately 15 to 20% chromium, 3% nickel, 0.10

to 1% magnesium and 0.20 to 0.50% carbon, with the remainder substantially iron.

6. A corrosion resisting steel containing approximately 10 to 15% chromium, 0.50 to 3% nickel and 0.10 to 3% magnesium, with the remainder substantially iron.

7. A corrosion resisting steel as defined in claim 6, containing approximately 0.10% carbon.

8. A corrosion resisting steel containing approximately 11 to 15% chromium, 1 to 3% nickel and 0.30 to 1% magnesium, with the remainder substantially iron.

9. A corrosion resisting steel containing approximately 10 to 20% chromium, 6 to 10% nickel, 0.15 to 3% of magnesiumand 0.10 to 0.20% carbon, with the remainder. substantially iron. v

10. A corrosion resisting steel containing approximately 15 to 18% chromium, 6 to 10% nickel and 0.30 to 1% magnesium, with the remainder substantially iron.

11. A corrosion resisting steel containing approximately 15 to 20%.chromium, 6 to 12% nickel, 0.15 to 3% of magnesium and 0.05 to 0.10% carbon, with the remainder substantially iron.

12. A corrosion resisting steel containing approximately 15 to 20% chromium, 8 to 10% nickel, 0.30 to 0.80% magnesium and 0.05 to 0.10% carbon, with the remainder substantially iron. 13. A corrosion resisting steel containing approximately 5% chromium, 3% nickel, 0.10 to 1% magnesium and 0.50% carbon, with the remainder substantially iron.

14. A corrosion resisting steel containing approximately 14'to 20% chromium, 0.50 to 3% nickel and 0.10 to 1% magnesium, with the remainder substantially iron.

15. A corrosion resisting steel containing approximately 14 to 20% chromium, 0.50 to 3% nickel and 0.10 to 1% magnesium, with the remainder substantially iron.

16. A corrosion resisting steel containing approximately 3 to 20% chromium, 0.25 to 12% nickel, and 0.05 to 3% magnesium, with the remainder substantially iron.

1'7. A corrosion resisting steel containing approximately 3 to 20% chromium 0.25 to 10% nickel, 0.10 to 3% magnesium with the remainder substantially iron.

18. A corrosion resisting steel containing approximately 10 to 20% chromium, 6 to 10% nickel, 0.10 to 3% magnesium and 0.10 to 0.20% carbon with the remainder substantially iron.

WILLIAM KEEN. 

